The overall objective of this project is to better understand the intensity coding in the auditory system. The studies are pursued along two main lines: intensity coding in the auditory system, and comparisons with the tactile system. Of interest are relationships between stimulus and response variables at threshold and superthreshold level in intensity, frequency and time domains, including interactions produced by multiple stimuli, such as arise in simultaneous and forward masking situations. In forward masking, emphasis will be placed on the loudness enhancement phenomenon, which may be related to one of the loudness-summation processes, as modulated by neural adaptation. There exists a controversy concerning psychophysically evident time constants in the auditory system. Experiments have been designed to resolve this controversy. Past auditory research on the project produced results suggesting effects of the olivo- cochlear efferent system. Some experiments will be aimed, therefore, at a determination if such effects took place in fact and, if the outcome is affirmative, the characteristics of the effects. Comparative studies of the auditory and tactile systems are aimed at intersensory generalities. Such generalities constitute the fundamental framework of advanced science. Past research on the project established two interrelated generalities which have been found to be valid in both auditory and tactle systems. According to one, just noticeable differences (jnds) in stimulus intensity are independent of the growth rate of subjective magnitude with stimulus intensity, when both subjective magnitude and the intensity are kept constant. According to the other, the jnds are equal when only the subjective magnitudes are equal within given oscillation frequencies. The generality of these findings is to be tested further. A mathematical theory has been developed on the project describing the relationship between the variability of subjective magnitude matches, such as in binaural loudness matching, and the slope of the matching function. The theory has been tested successfully in a limited number of auditory experiments. it is planned to test its validity more extensively in both the auditory and tactile systems. It is believed that the experiments planned for the project will contribute to the design of new clinical test, to a more accurate interpretation of existing tests and, especially with respect to forward masking experiments, to a better understanding of speech perception, with applications to hearing aid cochlear-implant technology.